Antimicrobial peptides: The ancient arm of the human immune system

The production of peptides and small proteins with microbicidal activity collectively called antimicrobial peptides (AMPs) is commonly considered to be a primitive mechanism of immunity and has been extensively studied in insects and other non-vertebrate organisms. In addition, a variety of AMPs present in amphibian skin secretion has been well characterised. There is now increasing evidence that AMPs play a crucial role in human immunity as well. Virtually all human tissues and cells typically exposed to microbes are able to produce AMPs. Important AMPs belonging to two structurally distinct classes, known as the defensins and the cathelicidins, are mainly produced by epithelial cells and neutrophils. AMPs…